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Institute: search.filters.UBSInstitut.Institut für Funktionelle Materie und QuantentechnologieAuthor: search.filters.author.Roth, Johannes

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Now showing 1 - 4 of 4
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    Atomistic simulation of ultra-short pulsed laser ablation of Al : an extension for non-thermalized electrons and ballistic transport
    (2022) Eisfeld, Eugen; Förster, Daniel; Klein, Dominic; Roth, Johannes
    For our model material aluminum, the influence of laser pulse duration in the range between 0.5 and 16 ps on the ablation depth is investigated in a computational study with a hybrid approach, combining molecular dynamics with the well known two-temperature model. A simple, yet expedient extension is proposed to account for the delayed thermalization as well as ballistic transport of the excited electrons. Comparing the simulated ablation depths to a series of our own experiments, the extension is found to considerably increase the predictive power of the model.
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    Classical interaction potentials for diverse materials from ab initio data : a review of potfit
    (2015) Brommer, Peter; Kiselev, Alexander; Schopf, Daniel; Beck, Philipp; Roth, Johannes; Trebin, Hans-Rainer
    Force matching is an established technique to generate effective potentials for molecular dynamics simulations from first-principles data. This method has been implemented in the open source code potfit. Here, we present a review of the method and describe the main features of the code. Particular emphasis is placed on the features added since the initial release: interactions represented by analytical functions, differential evolution as optimization method, and a greatly extended set of interaction models. Beyond the initially present pair and embedded-atom method potentials, potfit can now also optimize angular dependent potentials, charge and dipolar interactions, and electron-temperature-dependent potentials. We demonstrate the functionality of these interaction models using three example systems: phonons in type I clathrates, fracture of α-alumina, and laser-irradiated silicon.
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    Molecular dynamics simulations of the laser ablation of silicon with the thermal spike model
    (2021) Klein, Dominic; Eisfeld, Eugen; Roth, Johannes
    The purpose of this work is to model laser ablation of silicon on an atomistic scale in combination with a mesoscale model for the description of the electron-phonon interaction and an electron-temperature dependent interaction potential. The well-known continuum two-temperature model (TTM) for solids with highly excited electrons is extended from metals to silicon by explicitly taking charge carrier transport effects into account (nTTM). This is accomplished by the drift-diffusion limit of the Boltzmann-transport equation leading to the so called thermal-spike model (TSM). The model is further enhanced by extending the static modified Tersoff potential to a dynamical carrier excitation dependent interaction potential. We compare the TSM and nTTM with regard to physical correctness, numerical stability and applicability in the context of large-scale massive parallel high performance computing.
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    Prozessmodellierung in der additiven Fertigung : Molekulardynamische Simulation als Ansatz zur Optimierung der additiven Qualität
    (2023) Müller, Sarah; Klein, Dominic; Öhlschläger, Fabio; Roth, Johannes; Westkämper, Engelbert